Calibration of the Ms(VMAX) Technique in Eurasia
Abstract
We continue to develop and test the Matlab program EVALSURF, which estimates variable-period (8 less Tau less than 25 sec) Rayleigh-wave magnitudes using the Russell (2006) and M(s) (VMAX) measurement technique (Bonner et al., 2006a) for comparison to the historical formulas of Marshall and Basham (1972) and Rezapour and Pearce (1998). The program uses the updated Lawrence Livermore National Laboratory (LLNL) group velocity models (Pasyanos, 2005) to identify, phase match filter, and extract the fundamental mode Rayleigh waves for analysis. During the past year, we have used EVALSURF to: (1) estimate the surface wave magnitudes for the 9 October 2006 North Korean event, (2) examine the effects of large sedimentary basins on surface wave magnitudes, and (3) estimate surface wave magnitudes to periods as great as 40 seconds. We applied the EVALSURF (Bonner et al., 2006b) technique to the surface waves generated by the reported nuclear explosion detonated in North Korea on 9 October 2006. We feel confident that Rayleigh waves were observed at 12 stations at distance up to 40 degrees. The M(s) (VMAX) technique estimates a surface wave magnitude of 2.94 with interstation standard deviation of 0.17 magnitude units (m.u.). We found this estimate to be slightly above the Murphy et al (1997) event screening value (which is M(s)=2.90) for an International Data Center (IDC) m(b) of 4.1. If the m(b) is indeed accurate, this could suggest a convergence of the populations at small magnitudes (Sevens and Day, 1985); however, Bonner et al. (2006a) saw no evidence of the convergence at the Nevada Test Site for events of similar and smaller m(b). We examined the three-component records at each station and found no conclusive evidence that Love waves were generated and recorded.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2007
- Accession Number
- ADA519827
Entities
People
- David G. Harkrider
- Jessie L. Bonner
- Michael Pasyanos
- Michelle Johnson
Organizations
- Lawrence Livermore National Laboratory